The Impact of Listening with Directional Microphone Technology on Self-Perceived Localization Disabilities and Handicaps

The chief complaint of individuals with hearing impairment is difficulty hearing in noise, with directional microphones emerging as the most capable remediation. Our purpose was to determine the impact of directional microphones on localization disability and concurrent handicap. Fifty-seven individuals participated unaided and then in groups of 19, using omni-directional microphones, directional-microphones, or toggle-switch equipped amplification. The outcome measure was a localization disabilities and handicaps questionnaire. Comparisons between the unaided group versus the aided groups, and the directional-microphone groups versus the other two aided groups revealed no significant differences. None of the microphone schemes either increased or decreased self-perceived localization disability or handicap. Objective measures of localization ability are warranted and if significance is noted, clinicians should caution patients when moving in their environment. If no significant objective differences exist, in light of the subjective findings in this investigation concern over decreases in quality of life and safety with directional microphones need not be considered. La principal queja de los individuos con trastornos auditivos es la dificultad para escuchar en medio de ruido, emergiendo los micrófonos direccionales como el más capaz remedio. Nuestro propósito fue determinar el impacto de los micrófonos direccionales en la incapacidad de localización y en los impedimentos concurrentes. Cincuenta y siete individuos participaron sin amplificación y luego, en grupos de 19, utilizando micrófonos omni-direccionales, micrófonos direccionales, o amplificación equipada con interruptores de palanca. La medida de resultado fue un cuestionario de discapacidades e impedimentos de localización. Las comparaciones entre el grupo sin amplificación versus los grupos con amplificación, y entre el grupo con micrófono direccional versus los otros dos grupos con amplificación no revelaron diferencias significativas. Ninguno de los esquemas de micrófono aumentó o disminuyó la discapacidad o el impedimento auto-percibido de localización. Las medidas objetivas de la habilidad de localización se garantizan y si se llega a notar algo significativo, los clínicos deberían advertir a los pacientes cuando se desplacen en sus ambientes. Si no existen diferencias objetivas significativas, a la luz de los hallazgos subjetivos de esta investigación, no debe considerarse ninguna preocupación sobre la disminución de la calidad de vida o la seguridad con el uso de micrófonos direccionales.

Electrocochleography in the Evaluation of Patients with Ménière's Disease/Endolymphatic Hydrops

Electrocochleography (ECochG) has evolved as an important tool in the diagnosis/assessment/monitoring of Ménière's disease/endolymphatic hydrops (MD/ELH). This manuscript provides an update on the use of ECochG for these purposes. The material presented includes descriptions of the components of the electrocochleogram; ECochG recording approaches and parameters; how to prepare for an exam, including subject/patient considerations; construction and placement of a tympanic membrane recording electrode; and interpretation the electrocochleogram. Various approaches aimed at improving ECochG's sensitivity and specificity to MD/ELH also are described. These approaches go beyond simple measurement of the now-conventional summating potential (SP)/action potential (AP) magnitude ratio to include the SP magnitude to tonebursts, the SP/AP area ratio, and the AP latency difference to clicks of opposing polarity.

Validity, Internal Consistency, and Test/Retest Reliability of a Localization Disabilities and Handicaps Questionnaire

Psychometric evaluations were performed on a self-perceived localization disabilities and handicaps questionnaire. Twenty individuals with normal hearing bilaterally, twenty with profound unilateral hearing impairment (UHI), and ten with any degree of bilateral hearing impairment participated. Each subject completed the questionnaire. Comparisons of the responses of the subjects with normal hearing and those with UHI revealed significant differences among the groups for both disabilities and handicaps, establishing construct validity. Cronbach's Alpha correlational analyses of the responses of all subjects with hearing impairment revealed correlations of .900 (disabilities) and .800 (handicaps), establishing internal consistency. Each participant with hearing impairment was asked to complete the questionnaire again after three weeks. Pearson's correlational analyses of the responses at time one versus time two revealed correlations of .900 (disabilities) and .700 (handicaps), establishing test/retest reliability. This questionnaire is an appropriate tool for investigating the self-perceived localization disabilities and handicaps of individuals with hearing impairment.

Audiological Assessment of Word Recognition Skills in Persons With Aphasia

PURPOSE

The purpose of this study was to evaluate the ability of persons with aphasia, with and without hearing loss, to complete a commonly used open-set word recognition test that requires a verbal response. Furthermore, phonotactic probabilities and neighborhood densities of word recognition errors were assessed to explore potential underlying linguistic complexities that might differentially influence performance among groups.

METHOD

Four groups of adult participants were tested: participants with no brain injury with normal hearing, participants with no brain injury with hearing loss, participants with brain injury with aphasia and normal hearing, and participants with brain injury with aphasia and hearing loss. The Northwestern University Auditory Test No. 6 (NU-6; Tillman & Carhart, 1966) was administered. Those participants who were unable to respond orally (repeating words as heard) were assessed with the Picture Identification Task (Wilson & Antablin, 1980), permitting a picture-pointing response instead. Error patterns from the NU-6 were assessed to determine whether phonotactic probability influenced performance.

RESULTS

All participants with no brain injury and 72.7% of the participants with aphasia (24 out of 33) completed the NU-6. Furthermore, all participants who were unable to complete the NU-6 were able to complete the Picture Identification Task. There were significant group differences on NU-6 performance. The 2 groups with normal hearing had significantly higher scores than the 2 groups with hearing loss, but the 2 groups with normal hearing and the 2 groups with hearing loss did not differ from one another, implying that their performance was largely determined by hearing loss rather than by brain injury or aphasia. The neighborhood density, but not phonotactic probabilities, of the participants' errors differed across groups with and without aphasia.

CONCLUSIONS

Because the vast majority of the participants with aphasia examined could be tested readily using an instrument such as the NU-6, clinicians should not be reticent to use this test if patients are able to repeat single words, but routine use of alternative tests is encouraged for populations of people with brain injuries.

The Effect of Stimulus Intensity and Carrier Frequency on Auditory Middle- and Long-Latency Evoked Potentials Using a Steady-State-Response Approach

PURPOSE

The purpose of this study was to measure magnitude changes of auditory steady-state responses (ASSRs) and respective transient middle- and long-latency responses as a function of stimulus intensity and carrier frequency. The literature lacks clear consensus, including relationship to loudness.

METHOD

A cohort of 48 adults with normal hearing was examined from a companion study (Tlumak, Durrant, & Delgado, 2015) on effects of aging. ASSRs were elicited by repeated tone-burst stimuli presented at rates of 40 and 0.75 Hz at 3 frequencies and 5 levels of stimulus intensity. The design also permitted scrutiny of any gender bias to the results.

RESULTS

Similar to derived transient response findings, ASSR magnitude (harmonic sum) systematically increased with intensity. Input-output function only at 0.75 Hz approximated a log-log linear function. However, slopes fell well below that of doubling of loudness per 10 dB SPL. Results failed to demonstrate significance as a function of carrier frequency and gender for both repetition rates.

CONCLUSION

Effects of stimulus intensity, carrier frequency, and gender on ASSRs were similar to those of their transient counterparts. Findings remain disappointing for objective loudness estimation. Results suggest only a clear linkage to the long-latency response and the 0.75-Hz magnitude but require careful consideration of limitations/underlying mechanisms when measuring loudness-related effects.

The Effect of Advancing Age on Auditory Middle- and Long-Latency Evoked Potentials Using a Steady-State-Response Approach

PURPOSE

The purpose of the study was to objectively detect age-specific changes that occur in equivalent auditory steady-state responses (ASSRs), corresponding to transient middle- and long-latency auditory evoked potentials as a function of repetition rate and advancing age.

METHOD

The study included 48 healthy hearing adults who were equally divided into 3 groups by age: 20-39, 40-59, and 60-79 years. ASSRs were recorded at 7 repetition rates from 40 down to 0.75 Hz, elicited by trains of repeated tone burst stimuli.

RESULTS

Temporal analysis of middle- and long-latency equivalent ASSRs revealed no appreciable changes in the magnitudes of the response across the age groups. Likewise, the spectral analysis revealed that advancing age did not substantially affect the spectral content of the response at each repetition rate. Furthermore, the harmonic sum was not significantly different across the 3 age groups, between the younger adults versus the combined Older Group Sample 1 and Sample 2, and between the two extreme age groups (i.e., 20-39 vs. 60-79) for the middle- and long-latency equivalent ASSRs.

CONCLUSION

Advancing age has no effect on the long-latency equivalent ASSRs; however, aging does affect the middle-latency equivalent ASSRs when the mean age difference is ≥ 40 years.

Will diminishing cochlear delay affect speech perception in noise?

OBJECTIVE

Normal auditory systems appear well habituated to time/phase delays inherent to sound encoding along the hearing organ, sending frequency information non-simultaneously to the central auditory system. Eliminating, or simply perturbing, the cochlear delay might be expected to decrease speech recognition ability, especially under demanding listening conditions. Resources of a larger-scale investigation permitted a preliminary examination of this issue, particularly on a relevant timescale of empirically demonstrated cochlear delays.

DESIGN

In a randomized controlled trial study, word recognition was tested for mono-syllabic tokens treated digitally to exacerbate, if not diminish/nullify, such delays. Speech-weighted noise was used to interfere with listening to time-frequency reversed (nominally no delay) versus non-reversed (natural timing) transforms under three treatments of speech tokens: (1) original-digitally recorded; digitally processed to emphasize (2) transient versus (3) quasi-steady-state components.

STUDY SAMPLE

Ten normal-hearing young-adult females.

RESULTS

The findings failed to demonstrate statistically significant differences between delay conditions for any of the three speech-token treatments.

CONCLUSIONS

An algorithm putatively diminishing frequency-dependent cochlear delays failed to systematically deteriorate performance in all subjects for the fixed time-frequency transform, stimulus parameters, and test materials employed. Yet, trends were evident such that some effect of perturbing cochlear delays could not be ruled out completely.

Rinne Revisited

Objective

(1) Determine whether tuning fork material (aluminum vs stainless steel) affects Rinne testing in the clinical assessment of conductive hearing loss (CHL). (2) Determine the relative acoustic and mechanical outputs of 512-Hz tuning forks made of aluminum and stainless steel.

Study Design

Prospective, observational.

Setting

Outpatient otology clinic.

Subjects and Methods

Fifty subjects presenting May 2011 to May 2012 with negative or equivocal Rinne in at least 1 ear and same-day audiometry. Rinne test results using aluminum and steel forks were compared and correlated with the audiometric air-bone gap. Bench top measurements using sound-level meter, microphone, and artificial mastoid.

Results

Patients with CHL were more likely to produce a negative Rinne test with a steel fork than with an aluminum fork. Logistic regression revealed that the probability of a negative Rinne reached 50% at a 19 dB air-bone gap for stainless steel versus 27 dB with aluminum. Bench top testing revealed that steel forks demonstrate, in effect, more comparable air and bone conduction efficiencies while aluminum forks have relatively lower bone conduction efficiency.

Conclusion

We have found that steel tuning forks can detect a lesser air-bone gap compared to aluminum tuning forks. This is substantiated by observations of clear differences in the relative acoustic versus mechanical outputs of steel and aluminum forks, reflecting underlying inevitable differences in acoustic versus mechanical impedances of these devices, and thus efficiency of coupling sound/vibratory energy to the auditory system. These findings have clinical implications for using tuning forks to determine candidacy for stapes surgery.

Rinne Revisited: Steel versus Aluminum Tuning Forks

Objective: 1) Determine whether tuning fork material (aluminum vs stainless steel) affects Rinne testing in the clinical assessment of conductive hearing loss (CHL). 2) Determine the acoustic and mechanical impedance properties of 512 Hz tuning forks made of aluminum and stainless steel.

Method: Prospective, randomized observational study of 38 subjects presenting to outpatient clinic May 2011 through February 2012 with negative or equivocal Rinne and same-day audiogram. Laboratory tuning fork impedance measurements were obtained using sound-level meter and artificial mastoid (simulating air and bone conduction). Outcome: Sensitivity of negative Rinne in predicting air-bone gap at 500 Hz.

Results: Patients with CHL were more likely to produce a negative Rinne test with a steel fork than with an aluminum fork. Logistic regression revealed that the probability of a negative Rinne reached 50% at 20.3 (±2.5) dB air-bone gap for stainless steel versus 27.5 (±2.6) dB with aluminum. In a supporting laboratory study, steel forks exhibited comparable air and bone conduction efficiencies while aluminum forks favored air conduction. This results in a larger CHL being required to overcome aluminum forks’ increased air conduction efficiency before producing a negative Rinne.

Conclusion: We have found steel tuning forks are more sensitive in detecting the presence of an air-bone gap. This is substantiated by significant differences in the relative acoustic versus mechanical impedances of steel and aluminum forks. These findings have clinical implications for using tuning forks to determine candidacy for stapes surgery.

Steady-state analysis of auditory evoked potentials over a wide range of stimulus repetition rates in awake vs. natural sleep

OBJECTIVE

Auditory steady-state responses (ASSR) evoked by recurrent tones were assessed over a wide range of stimulus repetition rates embracing well the traditionally measured transient AEPs. Repetition rates of ≤ 10 Hz have received little attention in the context of the ASSR stimulus-response analysis approach which is speculated to provide technical advantages, if not additional/supplemental information, over more traditional transient stimulus-response paradigms.

DESIGN

Magnitudes were measured at repetition rates from 0.75 to 80 Hz, using trains of recurrent tone-burst stimuli.

STUDY SAMPLE

Twenty-five normal-hearing adults during sleep and awake.

RESULTS

Results show that response magnitudes for adults tested during sleep were significantly larger than those for adults while awake at repetition rates <5 Hz. Magnitudes were largest at the two lowest repetition rates, as expected from corresponding results obtained using conventional methods.

CONCLUSIONS

The analysis methods used in this paper may give information that will have applications for clinical testing. Results confirm and extend knowledge of the effects of repetition rate on AEPs over a range embracing the gamut of responses as traditionally classified, specifically at the beginning stages of natural sleep.

Validity and accuracy of electric response audiometry using the auditory steady-state response: Evaluation in an empirical design

The validity and accuracy of the application of the auditory steady-state response (ASSR) to electric response audiometry (ERA) was tested further in a study permitting subjects to be their own controls for hearing loss. Simulated sensorineural hearing loss (SSHL) of complex configuration and varying degrees was effected using filtered masking noise. Thresholds estimated via ASSR-ERA were compared to those measured via conventional pure-tone audiometry. Further, the slow vertex potential N1-P2 was recorded to permit a comparison with an evoked-response test of common content validity and known accuracy. Results in a homogeneous subject sample demonstrated strong interest correlation and agreement within 10 dB at 1000 to 4000 Hz (on average), but not at 500 Hz. The configurations determined by ASSR-ERA followed behavioral audiometric patterns well, except for the mildest degree of SSHL tested. Consequently, limitations of ERA remain, although ASSR-ERA appears to be quite valid overall and promises (justifiably) broad clinical applicability.

Analysis of counted behaviors in a single-subject design: modeling of hearing-aid intervention in hearing-impaired patients with Alzheimer's disease Análisis del conteo de conductas en un diseño unipersonal: Modelo de intervención con auxiliar auditivo en pacientes hipoacúsicos con enfermedad de Alzheimer

Clinical procedures related to patients with Alzheimer's Disease (AD) largely fail to address the patient's hearing. Given the challenges of this population, unconventional indicators of treatment efficacy may be required. Palmer et al (1999) reported on caregiver-tracked behaviors as outcome measures for hearing aid intervention. Using these data, hearing aid use and subsequent behavior was modeled as a first-order dynamic system, characterized by responses following an exponential time course. The results of such modeling suggest predictable outcomes of hearing aid intervention, or at least useful parameters of quantification (e.g. time-constant and steady-state response), permitting critical assessment of effects of intervention on negative behaviors versus hearing aid use, comparisons among behaviors, and/or comparisons of hearing-aid-use patterns and behavior counts among patients. Use in this and other difficult-to-test populations warrant further study to evaluate clinical efficacy of the analysis described.

Auditory steady-state responses (ASSR): effects of modulation and carrier frequencies

Presented are results relevant to extending the utility of the auditory steady-state response (ASSR) in threshold estimation at high-frequency carriers and to the accuracy of thresholds estimated using modulation frequencies near 40 versus 80 Hz. Initially, efforts were directed at confirming various findings reported in the literature apropos effects of several basic ASSR parameters. Results supplement others' observations suggesting that ASSR detection limits overestimate behavioral thresholds for conventional audiometric (carrier) frequencies from 500 to 4000 Hz. Further investigation revealed even greater errors of threshold estimates for 8000 and 12000 Hz, by about 14 and 22 dB on average, respectively. Although suggesting high-frequency ASSR testing to be efficacious, technical advances and additional work is needed to establish clinical utility. Comparison of effects of modulation frequency suggested ASSR thresholds with 40 Hz modulation to fall closer to behavioral threshold than those estimated at 80 Hz. Consequently, when circumstances permit, 40 Hz ASSR testing may be the method of choice (e.g. in the assessment of malingers, who may be tested awake/alert).

80 Hz auditory steady-state responses (ASSR) at 250 Hz and 12,000 Hz

Although measurement of the detection limits of the 80 Hz auditory steady-state response (ASSR) has proven to be a reasonably reliable tool in estimating hearing sensitivity in the mid-conventional audiometric frequencies (e.g. 1000 and 2000 Hz), results in the literature suggest potentially diminishing performance at 500 Hz and above 4000 Hz. The primary goal of this work was to examine the accuracy of threshold estimation via ASSR measurement for carriers more toward the audiometric extremes. At the same time, different stimulus and recording protocols than those commonly employed in ASSR testing were examined. Using a two-channel recording system, ASSRs were obtained from 15 normal-hearing young adults for an amplitude-modulated carrier of 250 Hz and repeated tone bursts of 10,000-16,000 Hz, gated using a Blackman window. Results attest to the ability to record ASSRs to a wide range of carrier frequencies but also suggest that accuracy of threshold estimation suffers toward the audiometric extremes. Feasibility of ASSR-based high-frequency audiometry is demonstrated in principle, but it is not clear that this method will permit adequate sensitivity and accuracy to support such applications as ototoxicity monitoring.

Parameters to maximize 2f2-f1 distortion product otoacoustic emission levels

PURPOSE

Past research has established parameters for the 2f1-f2 distortion product otoacoustic emissions (DPOAEs) that enhance response levels (e.g., L1 - L2 = 10 dB; f2/f1 = 1.22; L1, L2 = 65, 55 dB SPL). These same parameters do not optimize 2f2-f1 DPOAEs. Therefore, this study was conducted to evaluate more completely those parameters that produce the most robust 2f2-f1 output.

METHOD

Input-output functions of the 2f2-f1 component were obtained from 20 normal-hearing adults (with f2 = 2000 Hz and 4000 Hz). Frequency ratios, level differences, and overall sound levels were manipulated with parameter combinations chosen to expand on information established in previous studies. The DPOAE signal-to-noise ratio (SNR), response presence, and output levels were measured.

RESULTS

In general, mean SNRs and 2f2-f1 levels were greater, and DPOAEs were present more often for 2000 than for 4000 Hz across all parameter combinations. No single parameter combination resulted in pronounced maxima for 2f2-f1, which is consistent with past studies but is in sharp contrast to results for the more familiar 2f1-f2.

CONCLUSIONS

Overall, the results suggest that to maximize the 2f2-f1 level, lower test frequencies, low frequency ratio, essentially equal levels of primary tones, and moderate stimulus levels are best, and such parameters might be important for applying DPOAE measurement to assessment of normal and impaired auditory function.

Call for calibration standard for newborn screening using auditory brainstem responses

The mode of stimulation employed in newborn screening of the auditory brainstem response has evolved from the clinically standardized supraaural earphone to the tubal insert earphone, to most recently a circumaural earphone developed for this test. Considered here is the need to develop a standard for calibration of such devices for newborn screening applications, in particular. At risk is the prospect of missing the milder degrees of hearing loss, assuming a goal of detecting all clinically-significant congenital hearing losses. Two commercially manufactured test instruments for automated newborn screening were scrutinized via bench testing of sound output from their respective transducers, using a variety of measurements. By convention or design, none of the measurement approaches involved a model of the newborn ear, per se. While it was concluded that the manufacturers' method shows promise, namely as a relatively simple and potentially reliable method of calibration, concerns arose regarding output levels when measured according to both the manufacturers' and the authors' methods. Further work is needed to critically assess calibration methods and to establish, to the extent possible, appropriate norms and validation studies in newborns to provide a better understanding of the actual sound pressure level of the screening stimulus.

Cisplatin induces cytoplasmic to nuclear translocation of nucleotide excision repair factors among spiral ganglion neurons

Genomic DNA is a high-affinity target for the antineoplastic molecule cisplatin. Cell survival from cisplatin DNA damage is dependent on removal of cisplatin-DNA adducts by nucleotide excision repair (NER) pathways. The rate-limiting steps in the NER pathways are DNA damage identification and verification. These steps are accomplished by xeroderma pigmentosum complementation group C and A (XPC and XPA) and RNA polymerase II. Unlike RNA polymerase II, XPC and XPA have no known cellular function beyond DNA repair. Cisplatin is known to damage spiral ganglion neurons at the basal coil of the cochlea therefore it was posited that cisplatin may target their DNA and mobilize XPC and XPA. Female Fisher344 rats were given two, four day cycles of cisplatin (2mg/kg) or saline, separated by a 10day rest period. A 2 x 3 x 2 factorial design, consisting of two treatment conditions (cisplatin and saline treatment), three survival times (5, 19 and 22 days) and two analysis methods (quantitative RT-PCR and immunohistochemistry) was employed to evaluate the expression and distribution of XPC and XPA. Quantitative RT-PCR revealed statistically significant differences in cochlear XPC and XPA mRNA levels after cisplatin treatment at all times except day 22 for XPA. Immunohistochemistry revealed that a proportion ( approximately 50%) of spiral ganglion neurons in control rats showed cytoplasmic expression of XPC and XPA. After cisplatin treatment, a similar proportion ( approximately 50%) of spiral ganglion neurons showed increased nuclear expression of XPC and XPA, which appears to represent translocation from the cytoplasm. Basal coil spiral ganglion neurons translocated XPC and XPA at later treatment cycles and with less magnitude than apical coil neurons after cisplatin treatment. Therefore, it is suggested that cisplatin treatment induces nuclear translocation of NER proteins among spiral ganglion neurons and that this nuclear translocation is less efficient at the base relative to the apex.

Speech signal modification to increase intelligibility in noisy environments

The role of transient speech components on speech intelligibility was investigated. Speech was decomposed into two components--quasi-steady-state (QSS) and transient--using a set of time-varying filters whose center frequencies and bandwidths were controlled to identify the strongest formant components in speech. The relative energy and intelligibility of the QSS and transient components were compared to original speech. Most of the speech energy was in the QSS component, but this component had low intelligibility. The transient component had much lower energy but was almost as intelligible as the original speech, suggesting that the transient component included speech elements important to speech perception. A modified version of speech was produced by amplifying the transient component and recombining it with the original speech. The intelligibility of the modified speech in background noise was compared to that of the original speech, using a psychoacoustic procedure based on the modified rhyme protocol. Word recognition rates for the modified speech were significantly higher at low signal-to-noise ratios (SNRs), with minimal effect on intelligibility at higher SNRs. These results suggest that amplification of transient information may improve the intelligibility of speech in noise and that this improvement is more effective in severe noise conditions.

Reliability of electric response audiometry using 80 Hz auditory steady-state responses

The reliability of the Auditory Steady State Response (ASSR) has not been thoroughly evaluated despite its recent application as a clinical tool for threshold estimation. The purpose of this study was to examine test-retest (TR) reliability of ASSR threshold estimates in an empirical research design. The ASSR, tested using modulation frequencies approximately 80 Hz and above, was evaluated against pure tone audiometry (PTA), and the slow vertex potential (SVP, N1-P2). Sixteen normal-hearing young female adults were tested twice, one week apart. Varying degrees of sensorineural hearing loss of a notched configuration were simulated with filtered masking noise. Test-retest reliability was assessed using Pearson-product moment correlation analysis, supplemented by other post-hoc analyses. Results demonstrated moderately strong TR reliability for ASSR at 1000, 2000 and 4000 Hz (r = 0.83-0.93); however, the reliability of ASSR at 500 Hz was weaker (r = 0.75). Results suggest that ASSR-ERA is a reliable test at mid-high frequencies, at least with the configuration and degrees of simulated sensorineural hearing loss examined in this study.

Effect of intracochlear perfusion of vanilloids on cochlear neural activity in the guinea pig

Recent findings show that the vanilloid receptor subtype 1 (TRPV1) is expressed by cochlear outer hair cells and spiral ganglion cells, and that its expression is up-regulated in ganglion cells after aminoglycoside treatment. This study tested the hypothesis that agents that act on TRPV1 receptors affect the spectrum of ensemble background activity (EBA). Consecutive intracochlear perfusions of the TRPV1 agonist, capsaicin (CAP 0.1, 1, and 10 parts per million), as well as its antagonist capsazepine (CZP), were used to test effects of TRPV1 activation on EBA recorded from the cochlear base. Perfusion with CAP alone produced a dose-dependent increase of the 900-Hz peak ratio (power normalized re the overall spectrum) of the EBA. The CAP effect was attenuated during concurrent perfusion with CZP. These findings are consistent with the hypothesis that TRPV1 activation increases background activity of spiral ganglion cells and support a role of TRPV1 in gating spontaneous and evoked auditory nerve excitability.

Study of auditory function in patients with chronic obstructive pulmonary diseases

This study was designed to measure auditory function in patients with chronic obstructive pulmonary diseases (COPDs) who generally suffer from chronic hypoxemia. Control and COPD subject groups received a battery of tests to assess overall hearing sensitivity and peripheral (end-organ and eighth-nerve) and brain-stem auditory function, as well as blood-gas analysis. Results showed a statistically significant difference for all audiological measures between the control group and a COPD subgroup--the presumptive hypoxic subjects (partial oxygen tensions, PO2, <75 mm Hg). Correlation analyses of results from all subjects (regardless of PO2) also revealed significant covariance with PO2 for overall, RMS, amplitude of click-evoked otoacoustic emissions (RA), hearing threshold level, and auditory brain-stem response (ABR, I-V inter-peak latency). Chi2 or Fisher's exact tests were statistically significant for frequencies of cases classified according to a criterion PO2 of 70 mm Hg (putative critical O2 for completely normal auditory function) and either hearing thresholds falling below or RA values above 1.5 standard deviations of the control-group means, respectively. However, chi2 was not significant for a comparable criterion of ABR I-V IPL. In general, clinically significant hearing loss was uncommon in COPD patients, and the observed effects represented relatively small changes in the auditory measures examined. Still, overall, changes were in the direction of poorer function, and these results suggest physiologically significant impact of chronic hypoxemia and the need for further study to evaluate thoroughly this medical condition as a potential risk factor for audio-vestibular dysfunction.

An algorithm for analyzing linkages affected by heterozygous translocations: QuadMap

Heterozygous chromosome rearrangements such as reciprocal translocations are most accurately displayed as two-dimensional linkage maps. Standard linkage mapping software packages, such as MapMaker, generate only one-dimensional maps and so reciprocal translocations appear as clusters of markers, even though they originate from two nonhomologous chromosomes. To more accurately map these regions, researchers have developed statistical methods that use the variance in map distance to distinguish among the four segments (two translocation, two interstitial) of the translocation. In this study, we describe modifications to one of these protocols, that proposed by Livingstone et al. (2000). We also introduce QuadMap, a new software application for dissecting heterozygous translocation-affected linkage maps.

Lateralization of the effects of the benzodiazepine drug oxazepam on medial olivocochlear system activity in humans

Benzodiazepines (Bzd) are known to interact with GABAergic inhibitory neurotransmission. Previous research on their effect on human auditory efferent pathways--through evoked otoacoustic emissions suppression by contralateral acoustic stimulation (CAS)--indicated a decrease in medial olivocochlear (MOC) efferent system inhibitory activity, after oral intake of oxazepam--representative of the Bzd drug class. To date, this pharmacological effect was only assessed in the right ear. Since a leftward asymmetry of Bzd receptors localization in human auditory cortex has been described recently, we explored in this study the hypothesis of an asymmetrical action of Bzd on MOC efferent functioning. The results revealed a significant difference of Bzd effect probing the right ear versus the left ear, with CAS-induced suppression being less effective in the right than left ear after oxazepam intake. This finding raises the question of possible neurochemical left-right asymmetry in the descending auditory pathways. The potential localization of this asymmetry is discussed.

Auditory steady-state response evaluation of auditory thresholds in cochlear implant patients

The aims of this work were to characterize the electrophysiologic response obtained by measurement of the auditory steady-state response (ASSR) in patients with a cochlear implant (MXM Digisonic) and to study the relationship between the subjective thresholds of the implantees and those estimated using electrical auditory steady-state response (ASSR)-based objective audiometry. Five subjects were examined with the use of four carrier frequencies--600, 1000, 2000 and 3500 Hz--modulated at frequencies between 70 and 85Hz, a particular frequency of modulation being represented at a specific electrode (for each carrier frequency) as a particular pulse-width modulation frequency. The protocol consisted of testing output and thresholds for different overall pulse durations for several stimulus (pulse) intensities, rendering multiple threshold measures (in duration) for each subject tested. The non-linearity of response growth, as a function of duration, provided the basis for teasing apart physiologic response and electrical artefact in the suprathreshold recorded responses. Thresholds estimated with use of the electrical ASSR demonstrated reasonably good agreement with the subjective thresholds. The results obtained thus demonstrated the efficacy of the approach and are encouraging for further advances in cochlear implant applications.

Effect of stimulus frequency and stimulation site on the N1m response of the human auditory cortex

The aim of the present study was to investigate the functional organization of the auditory cortex for pure tones of 1, 2, 4, 6, 8 and 12 kHz. Ten subjects were tested with a whole-head magnetometer (151 channels). The location, latency and amplitude of the generators of the N1m (the main component of the response, peaking approximately at 100 ms) were explored simultaneously in the right and left hemispheres under monaural stimulation. Our results revealed that tonotopy is a rather complex functional organization of the auditory cortex. From 1 to 12 kHz, tonotopic maps were found for contralateral as well as for ipsilateral stimulation: N1m generators were found to be tonotopically organized mainly in an anterior-posterior direction in both hemispheres, whatever the stimulated ear, but also in an inferior-superior direction in the right hemisphere. Furthermore, latencies were longer in the left than in the right hemisphere. Two different representations of spectral distribution were found in the right auditory cortex: one for ipsilateral and one for contralateral stimulation.

Development of f2/f1 ratio functions in humans

Otoacoustic emissions (OAEs) presumably represent active processes within the cochlea fundamental to frequency-selectivity in peripheral auditory function. Maturation of the cochlear amplifier, vis-a-vis frequency encoding or selectivity, has yet to be fully characterized in humans. The purpose of this study was to further investigate the maturation of features of the f2/f1 frequency ratio (Distortion Product OAE amplitude X f2/f1 ratio) presumed to reflect cochlear frequency selectivity. A cross-sectional, multivariate study was completed comparing three age groups: pre-term infants, term infants and young adult subjects. Frequency ratio functions were analyzed at three f2 frequencies--2000, 4000 and 6000 Hz. An analysis included an estimation of the optimal ratio (OR) and a bandwidth-like measure (Q3). Analysis revealed significant interactions of age x frequency x gender for optimal ratio and a significant interaction of age x frequency for Q3. Consistent and statistically significant differences for both OR and Q3 were found in female subjects and when f2 = 2 or 6 kHz. This supports research by others [Abdala, J. Acoust. Soc. Am. 114, 3239-3250 (2003)] suggesting that the development of cochlear active mechanisms may still be somewhat in flux at least through term birth. Furthermore, OAEs appear to demonstrate gender differences in the course of such maturational changes.

Effects of interaural frequency difference on binaural fusion evidenced by electrophysiological versus psychoacoustical measures

The binaural interaction component (BIC=sum of monaural-true binaural) of the auditory brainstem response appears to reflect central binaural fusion/lateralization processes. Auditory middle-latency responses (AMLRs) are more robust and may reflect more completely such binaural processing. The AMLR also demonstrates such binaural interaction. The fusion of dichotically presented tones with an interaural frequency difference (IFD) offers another test of the extent to which electrophysiological and psychoacoustical measures agree. The effect of IFDs on both the BIC of the AMLR and a psychoacoustical measure of binaural fusion thus were examined. The perception of 20-ms tone bursts at/near 500 Hz with increasing IFDs showed, first, a deviated sound image from the center of the head, followed by clearly separate pitch percepts in each ear. Thresholds of detection of sound deviation and separation (i.e., nonfusion) were found to be 57 and 209 Hz, respectively. However, magnitudes of BICs of the AMLR were found to remain nearly. constant for IFDs up to the 400-Hz (limit of range tested), suggesting that the AMLR-BIC does not provide an objective index of this aspect of binaural processing, at least not under the conditions examined. The nature of lateralization due to IFDs and the concept of critical bands for binaural fusion are also discussed. Further research appears warranted to investigate the significance of the lack of effect of IFDs on the AMLR-BIC. Finally, the IFD paradigm itself would seem useful in that it permits determination of the limit for nonfusion of sounds presented binaurally, a limit not accessible via more conventional paradigms involving interaural time, phase, or intensity differences.

Development of auditory asymmetry in transient evoked otoacoustic emissions in pre-term infants

We previously reported that transient evoked otoacoustic emissions (TEOAEs) continue to develop after the onset of cochlear function in pre-term infants from 34 to 39 weeks of conceptional age (Morlet et al., 1996). The time-course of development differed between genders. Reported here are findings of further analysis of data from the study cohort, comprising 1020 ears of 510 pre-term neonates (conceptional age ranging from 34 to 39 weeks), demonstrating developmental differences between right and left ears. The left ear of female pre-term infants showed enhancement of TEOAE amplitude at low and medium frequencies with age, whereas differences were less dramatic in the right ear. In male infants, TEOAE amplitude decreased in several frequency bands at high frequencies, above 4 kHz, between 34 and 39 weeks conceptional age; most developmental differences were found to be more dramatic in the right than in the left ear. It is tempting to speculate that these developmental features underlie well-known inter-aural asymmetries that have been demonstrated in the adult human.

Stacked tone-burst-evoked auditory brainstem response (ABR): preliminary findings

In 1997, Don and his co-workers described a new method for evaluating the auditory brainstem response (ABR)--yielding the stacked-wave-V ABR--which may permit the reliable detection of even small vestibular schwannomas (VSs). However, this method requires a masking technique that may not be readily available to the clinician. Furthermore, relatively high-level noise is required and may be annoying to the patient. An alternative method that might permit the same manipulation of the ABR was thus explored whereby tone-bursts (TBs) were used to obtain frequency-specific ABRs. The goal of the study was to determine whether TBs could be used to achieve the sort of de-convolution and subsequent enhancement of wave V reported with the original method of Don et al. First, the TB-stacked ABR (wave V) was compared to that obtained using derived narrowband masked ABRs in young normal-hearing subjects. Second, the TB method was employed in subjects with unilateral VSs and in patients with unilateral sensory hearing loss in a preliminary clinical trial. The observed results are promising for the use of the TB method as an alternative approach to ABR 'stacking' and warrant further research and development of the TB method.

Toward a better understanding of the perception of self-produced speech

The subject of how humans hear their own voices while speaking has received sporadic attention. Previous investigations suggest that the voice is heard substantially via bone conduction, implying a different transfer function to the ear--perhaps a low-pass filter--than for purely air-conducted vocalizations. Determining the characteristics of the transfer function of self-produced speech might contribute to a better understanding of self-perception. Such information may have important implications for treating articulation disorders. The efficacy of training discrimination during the remediation of articulation disorders remains unclear, perhaps because clients are asked to discriminate either speech of others or recorded self-speech samples not readily recognized as their own. This study was conducted to determine preference for filtered self-monitored speech in a delayed feedback paradigm. Participants made immediate comparisons of their real-time speech to delayed-recorded filtered self-speech samples. Participants demonstrated a clear preference for low-pass filtered speech, supporting earlier findings, but we were unable to determine the transfer function itself.

LEARNING OUTCOMES

As a result of this activity, the learner will be able to describe some reasons why an individual's tape recorded speech typically sounds different to him/her from his/her own, live speech. As a result of this activity, the learner will be able to describe some potential applications for an accurately-characterized transfer function for self-produced speech.

Frequency and temporal analysis of contralateral acoustic stimulation on evoked otoacoustic emissions in humans

Previous studies have shown that the effect of contralateral acoustic stimulation (CAS) on ipsilateral evoked otoacoustic emissions (EOAE) depends somewhat upon the spectrum of the eliciting stimulus. The latency of the EOAE, however, is itself frequency-dependent. Consequently, two general ways of analyzing the effects of CAS may be considered: by frequency band or by temporal segment. In this study, we analyzed the effects of CAS both ways in the same subjects, essentially simultaneously. The frequency analysis of the EOAE derived from the wavelet transform (WT). The WT is known to provide a robust approach to the analysis of non-stationary signals and was anticipated to avoid possible time-frequency confounds of the cochlear mechanical system. For comparison, a more basic analysis - using a temporal moving window - was employed. The results largely support earlier findings and confirm that in humans the greatest suppression of EOAEs by CAS is obtained for lower frequency and/or longer latency EOAE components. Despite expectations for the WT analysis, the more basic, temporal, analysis tended to yield the clearer results.

Somatosensory cuing of head-only rotational testing

Head-only rotational testing (HORT) is a method of assessing the vestibulo-ocular reflex (VOR) that can be performed at the bedside with inexpensive, transportable equipment. Previous studies of HORT using auditory cuing have suggested that test results are in large part independent of the method by which a subject's head is moved, that is, active versus passive. However, many subjects have difficulty moving their head at rotational frequencies of 3 Hz or greater. In an attempt to overcome this difficulty, and to learn more about HORT, we explored the possibility of providing subjects with a somatosensory, rather than an auditory cue for head movement. Somatosensory, cues were provided either by applying gentle pressure against a tightly-fitted headband or by lightly tapping on the shoulders. Our results with young, healthy subjects indicate that somatosensory cuing is an efficacious means of inducing periodic head rotation and that HORT results are unaffected by the type of cue provided. We conclude that somatosensory rather than auditory cuing may be the preferred method of performing HORT.

Accuracy of hearing aid use time as reported by experienced hearing aid wearers

OBJECTIVE

The purpose of this study was to investigate the relationship between the amount of time that a person reports wearing his or her hearing aid and the actual time that the hearing aid is worn. Although use time data are used in the analysis and interpretation of investigations concerned with auditory perceptual learning and with user satisfaction, the accuracy of self-reported use time has not been fully investigated.

DESIGN

The experimental and control group were fit with a hearing aid that has the capability of storing use time data for later analysis. The experimental group was told that the self-reported use time would be verified with a computer analysis of the hearing aid that provides the actual use time. The control group was not informed of the use time validation procedure. The agreement between self-reported and actual use time was compared statistically between groups (knowledge of validation versus no knowledge of validation).

RESULTS

The experimental group provided accurate self-reported use time whereas the control group showed a significant difference between actual use time and self-reported use time.

CONCLUSIONS

The results may assist in the interpretation of results of previous investigations that have depended on self-reported use time and in the design of future investigations. For the clinician, the results indicate that relying on a patient's self-reported hearing aid use time for documentation of satisfaction or signal processing preference may be misleading.

Somatosensory cuing of head-only rotational testing

Head-only rotational testing (HORT) is a method of assessing the vestibulo-ocular reflex (VOR) that can be performed at the bedside with inexpensive, transportable equipment. Previous studies of HORT using auditory cuing have suggested that test results are in large part independent of the method by which a subject's head is moved, that is, active versus passive. However, many subjects have difficulty moving their head at rotational frequencies of 3 Hz or greater. In an attempt to overcome this difficulty, and to learn more about HORT, we explored the possibility of providing subjects with a somatosensory, rather than an auditory cue for head movement. Somatosensory, cues were provided either by applying gentle pressure against a tightly-fitted headband or by lightly tapping on the shoulders. Our results with young, healthy subjects indicate that somatosensory cuing is an efficacious means of inducing periodic head rotation and that HORT results are unaffected by the type of cue provided. We conclude that somatosensory rather than auditory cuing may be the preferred method of performing HORT.

Head-Only Rotational Testing in the Elderly

Head-only rotational testing (HORT) is a noninvasive technique to assess the vestibulo-ocular reflex (VOR) that can be performed in a nonlaboratory environment with inexpensive, portable equipment. Little data are available regarding the applicability of this technique to the elderly in whom limitations of cervical range of motion might reduce the usefulness of the technique. This study was designed to apply HORT to a small group of normal elderly subjects to determine whether the technique could be used successfully in this population. Also, the VOR parameters derived from HORT were compared with the results obtained from a group of healthy young control subjects. HORT was performed both with and without visual fixation of an earth-fixed target, using both active head movement and passive head movement. Results indicated that the responses of the elderly were indistinguishable from those of the young except for a slightly higher gain at 1 Hz in the young subjects. Other findings, consistent across young and elderly, were that visual fixation increased gain and decreased phase lead at lower frequencies and that VOR parameters were unaffected by volition, that is, active and passive head rotation produced similar responses. These findings suggest that HORT can be applied to the elderly without difficulty. Future studies will assess the usefulness of HORT in elderly patients with VOR disorders.

Head-only rotational testing in the elderly

Head-only rotational testing (HORT) is a noninvasive technique to assess the vestibuloocular reflex (VOR) that can be performed in a nonlaboratory environment with inexpensive, portable equipment. Little data are available regarding the applicability of this technique to the elderly in whom limitations of cervical range of motion might reduce the usefulness of the technique. This study was designed to apply HORT to a small group of normal elderly subjects to determine whether the technique could be used successfully in this population. Also, the VOR parameters derived from HORT were compared with the results obtained from a group of healthy young control subjects. HORT was performed both with and without visual fixation of an earth-fixed target, using both active head movement and passive head movement. Results indicated that the responses of the elderly were indistinguishable from those of the young except for a slightly higher gain at 1 Hz in the young subjects. Other findings, consistent across young and elderly, were that visual fixation increased gain and decreased phase lead at lower frequencies and that VOR parameters were unaffected by volition, that is, active and passive head rotation produced similar responses. These findings suggest that HORT can be applied to the elderly without difficulty. Future studies will assess the usefulness of HORT in elderly patients with VOR disorders.

Managing hearing loss in a patient with Alzheimer disease

This case study reports the management of hearing loss in a patient with Alzheimer disease (AD) living at home with a spouse care giver. The report highlights the interaction between symptoms associated with AD and hearing loss and the lack of data regarding remediation of hearing loss in this population. Specifically, the case illustrates the modifications in evaluation and verification of the hearing aid fitting that may be advisable when working with patients with AD. The data for this patient illustrate some novel measurement techniques that may assist the professional in documenting the impact of treatment in this population.

Are inner or outer hair cells the source of summating potentials recorded from the round window?

The relative contribution of inner hair cells (IHCs) and outer hair cells (OHCs) to the production of the summating potential (SP) is unresolved in the literature. Since OHCs in the base of the cochlea have been reported to produce little dc receptor potential except at very high sound pressure levels [I. J. Russell and P. M. Sellick, J. Physiol (London) 284, 261-290 (1983)], the IHCs appear to be the dominant source of the SP. However, results of intracochlear recordings are conflicting, although deriving from measurements in different turns of the cochlea [e.g., I. J. Russell and P. M. Sellick, J. Physiol. (London) 284, 261-290 (1983) versus P. Dallos and M. A. Cheatham, Sensory Transduction (1992)]. To determine which type of hair cells is the dominant source of the SP recorded at the round window, we used carboplatin to selectively destroy IHCs or a combination of IHCs and OHCs in the chinchilla. Related work, using measurements of distortion product otoacoustic emissions and cochlear potentials to assess the functional status of the OHCs served to validate this animal model [Trautwein et al., Hearing Res. 96(1-2), 71-82 (1996)]. The SP, cochlear microphonic (CM), and compound action potential (CAP) were recorded from the round window, and cochleograms were determined using well-established histological methods. The results were reasonably distinctive among three groups of ears--control (from untreated normal chinchillas), IHC-loss (extensive IHC loss with minor or no loss of OHCs), and IHC-OHC loss (total IHC loss plus extensive loss of OHCs over the basal half of the cochlea). Ears of chinchillas in the IHC loss group had a decrease of over 50% in SP output compared to control ears with the exact reduction depending somewhat upon the stimulus conditions. Ears in the IHC + OHC loss group, nevertheless, showed even further reduction in SP output which was clearly attributable to destruction of OHCs in the cochlear base. It was concluded that, although the IHCs are responsible for a greater contribution of dc-receptor potential to the SP recorded at the round window, a significant contribution is made by the OHCs, as well. The results suggest, specifically, that the round window "sees" SP output roughly in inverse proportion to the IHC:OHC. Lastly, the complexity of SP production, as recorded from the round window, precludes a completely straightforward interpretation of the SP:CAP in clinical ECochG.

Evaluation of the nonorganic hearing loss suspect

OBJECTIVE

To examine the utility of distortion-product otoacoustic emissions (DPOAEs) in the assessment of the nonorganic suspect because DPOAE analysis constitutes an objective test of hair-cell function that yields audiometriclike data.

STUDY DESIGN

Retrospective study of clinical findings.

SETTING

Audiology outpatient clinic of our university's medical center.

PATIENTS

The study cohort comprised 30 patients who presented with a profile of suspicion for nonorganic hearing loss. Most cases were found, with the aid of DPOAE testing, to be nonorganic or to have nonorganic overlays to organic hearing loss.

INTERVENTIONS

Interventions were diagnostic only.

MAIN OUTCOME MEASURES

Observed audiometric findings and changes thereof.

RESULTS

Statistically significant decreases in thresholds occurred in subgroups of those cases deemed to be truly nonorganic in origin.

CONCLUSIONS

Especially considering test efficiency, the results support the inclusion of DPOAE analysis in the diagnostic management of the suspect-nonorganic patient.

Surface dependence: a balance control strategy in panic disorder with agoraphobia

OBJECTIVE

Previous studies have reported vestibular dysfunction and impaired balance in patients with agoraphobia. Vestibular dysfunction may lead to an information processing strategy focusing on spatial stimuli from two nonvestibular sensory channels, vision and proprioception. This nonvestibular balance control strategy may in turn lead to discomfort in situations involving inadequate visual or proprioceptive spatial cues (space and motion discomfort). The objective of this study was to examine sensory integration of spatial information in agoraphobia. Because of previous findings that space and motion discomfort and vestibular dysfunction are common in agoraphobia, we hypothesized that agoraphobics would use a nonvestibular balance control strategy.

METHOD

Using computerized dynamic posturography, we examined balance performance in patients with panic disorder with agoraphobia, uncomplicated panic disorder, nonpanic anxiety disorders, and depression without anxiety, as well as healthy subjects for comparison. The posturography procedure included six sensory conditions in which visual and proprioceptive balance information was manipulated experimentally by permutations of sway-referencing the support surface or the visual surround or by having patients close their eyes.

RESULTS

The agoraphobics had impaired balance when proprioceptive balance information was minimized by sway-referencing the support surface (p < 0.02). This pattern, called surface dependence, tended to be more pronounced in agoraphobics who reported space and motion discomfort, including fear of heights or boats.

CONCLUSION

Agoraphobics rely on proprioceptive cues for maintenance of upright balance. This strategy may lead to intolerance of situations characterized by unstable support.

Development of cochlear active mechanisms in humans differs between gender

Despite onset of function early during the third term of gestation, the human auditory system demonstrates continued maturation, thought previously to occur primarily at the neural level. The electromotile properties of outer hair cells appear to contribute substantially to hearing sensitivity and frequency selectivity and lead to the generation of otoacoustic emissions (OAEs). This report demonstrates continued development of cochlear active mechanisms (i.e. end-organ level) after onset of cochlear function, as reflected by OAEs. Significant gender differences also are reported, corresponding to recently observed intersex differences in cochlear length and precursory to gender differences observed in the adult.